Slotted turbine blade



1952 E. A. STALKER SLOTTED TURBINE BLADE 3 Sheets-Sheet 1 Filed Jan. 24, 1947 ym/Mm Oct. 14, 1952 STALKER 2,613,910

SLOTTED TURBINE BLADE Filed Jan. 24, 1947 :5 Sheets-Sheet 2 INVEN TOR.

iamm $241406 Oct. 14, 1952 E. A. STALKER SLOTTED TURBINE BLADE 3 Sheets-Sheet 5 Filed Jan. 24, 1947 a INV NTOR.

Patented Oct. 14, 1952 SLOTTED TURBINE BLADE Edward A. Stalker, Bay City, Mich. Application January 24, 1947, Serial No. 724,103

This invention relates to turbine, blades and particularly to turbine blades incorporating means to keep them cool.

In my patent application, Serial No. 510,834 filed November 19, 1943, now Patent No. 2,489,683 issued November 29, 1949, I have disclosed a blade having nose slots for the emission of a cooling layer of fluid which is emitted in such a manner as tointerpose itself as .an insulating layer between, the hot motive gases of the turbine and the blade wall. j

The present invention is directed to a blade construction by which the slots can be incorporated into the blade practically and economically. '.An' object of this invention is to provide a turbine blade with a specially formed slot.

; Still another-object is to provide a blade strucs- Claims. (01. 253-3915) ture ,with slots'which is practical and economical to make.

1- The above objects are accomplished by the meansillustrated in the accompanying drawings in which- 1 Figure 1 is a perspective of a blade. showing the nose slots;

- Figure 2 is a spanwise section taken along line 2+2 in Fig. 3; i

Figure 3 is a chordwise section along line 3'3 inFig.l;- w

Figure 4 is a plan view of a sheet before forming'into ablade; 1

Figure 5 shows the of Fig.4 into ablade; Figure 6' is a fragmentary section along line 6-6 in Fig.4; I

Figure '7 illustrates a tubular blank for use in another method of forming the'blade;

Figure 8 is a fragmentary view of the blan showing the platelets cut on the blank; 1

Figure'9 is a fragmentary section 'taken' along the1ine9-9inFig.8; I q 0 Figure 110 shows the platelets of Fig. 9 bent down to form narrow slots .therebetween';

steps of bending the sheet Figure ll-is a fragmentary perspective -view of the blade as viewed looking toward the. nose;

Figure 12 is a section along line l2'-I2lin Fig 11; and

Figure 13 shows a blade blank being slotted by a conical'saw. I Referring particularly to the drawings Figs. 1'

to 3 show the desired form of the turbine blade.

The blade [0 is composed of the surface l2 and the blade hub 14, t e former being welded to the lattercatthe localities l6 and I8.

The blade is hollow and carries within a cooling fluid flow, preferably air which is discharged through thenose slots 20.

The nose slots are formed by overlapping sid walls ofthe platelets forming slots which extend substantially transversely to theleading edge or span of the blade and with legs en both pl and lower surfaces ofthe blade having a span-jwise component of direction toward the ame end of the blade 1. e,, away from the end having the fluid admission opening. The slots arelthus crescent or chevron shaped to direct the slot flow 26 along the blade surface, both spanwise-and chordwise and along both 'upper'and lower surfaces for a wide range of locations of the stagnation point 28 of the 'main flow 24. c The fluid emitted from the slots provides an insulating layer of cooler air between th hot gases of the turbine and the wet-11s of the blade. This shape provides for the properfunctioning of" the protective flow for the stagnation point on either the upper or lower surface of the nose. I'he theory of this insulating layer has been discussed in my pending application mentioned earlier. j "j Since the slot walls must be formed to direct the flow along the blade surface the platelets 30 which overlap to form the slots should b'e'curved chordwise and the portion of the slot wall 'oyer lapped by the opposite wall must have a generous radius in order to insure that the flow follows the surface without separating therefrom. .{It is diflicult to achieve such slot formbut the present invention discloses a blade in which this is accomplished in an economical and practical man ner.

Inone form of the invention, Figs. 4 to 61a sheet or blank 40' of metal is formed with as'ub stantial thickening or hump 42. '"By suitable milling, sawing or the like, the slots 1.20 are formed in'the hump, giving a chevronlike appearance to'the blank along the hump. Next the blank is bent or folded and forced into the shape of the blade l2 as shownin Figf5 through intervening steps such as. '1 The'edges or the blank are joined as by welding together at the trailing edge 46;

The side walls of the slots which aretheplate lets 30 are pressed or forged tohavethe'nose curvature of the blade. 7 w

In another form' of the invention shownin Figs. 7 to 12, a tubular blank is formed with a nose hump 62 extending along "the tube, axis.

. by .the appended claims. 7

is deformed into the blade shape shown in Fig. 11

which is similar to that shown in Fig. l where the blade isequipped-with the blade hub. l4.

Fig. 12 shows that the platelets'are curved properly in the chordwise direction along the overlapped portions which is very important.

Fig. 12 also shows the blade cross section with:

the thickening 64' shown dotted at the trailing edge. This portion 54 after the main shape of theblade has been established is cut off togive the sharp trailing edge rather than a blunt or rounded one, and the interior is well rounded at 72 so as to preclude fatigue failures which ordinarily start at acute angles in the surface.

. In still a'nother. form of the: invention; shown "fluid providing an insulating layer of air on the blade surface to exclude heat from turbine gases. 2. In combination to form a slotted turbine "blade, a sheet metal tube having a blade cross section, and inclined spaced platelets disposed spanwise along the nose-portion of said tube, said in Fig 13 the. tubular blade blank 86: isformed with a thickened wall 82 at. the nose, V The slots 84 in. the nose are cut witha conicalsaw. That isfthe saw blade 85 is conical with acircular cross section andthe teeth are cut in the small diameter; end.v The saw blade is rotated'about -the axis 190of.-the. cone and is fed intothe work along-the direction 92 parallel toone side of the cone.

IThel saw cuts a slot curved chordwise in the turbine bladev nose and inclined to the nosesurface. These slots are .cut'through thethickness of the nose wallto establish communication with the spanwise slot 94 cut in thenose to extend spanwise- The slots are fed air from the interior of the turbine blade.

. In. the practical case with small turbine blades they saw will out too wide a slot sincethe saw bladethickness. becomes impractical when re.- ducedto a few thousands ofan inch. There: fore the slots are cut in a practical size and subsequently the walls of each slot are pressed: together to producethe correct slot width. 7 In. Fig. 13 I. have shown a blade blank already formed into a'blade section into which the saw iscutting. .The blank could be a circular tube 'whichywouldbe deformed into a blade section after the slots are out. M

InFig. I3 I. have shown a saw having teeth out on thejend ofacohical surface. However this surface couldbe a cylindrical surface or, any other curved surface with the teeth in the free end. .Preferably the toothed contour is closed for insuring the strength of the tool buta segment of such a curved surface could also be employed. I call such tools curved end cutters.

\ It willnow be clear that I. have disclosed a novel and useful turbine blade which can be I maintained in a relativelycool state in the hot motivegasflow through the turbine, and I have described a practical and economical method of producing. such a blade with proper slot width and form in boththe spanwise and chordwise directions... H

While Ihave illustrated a specific form of this invention it is to be understood that I.do.not intend to limit myself to this exact form but intendto claim.- my invention broadly as indicated I claim:

1.. In combination to form a slotted turbine blade, a sheet metaltube having a'blade cross section,.said tubehaving inclined spaced platelets. disposedspanwise along said tube and fixed thereto, each said platelet lapping. a spanwise from exterior hot gas.

platelets-being curved in the chordwise direction, each said platelet lapping a succeeding platelet to forma' slot therebetween havinglegs on bothiupper and lower surfaces of the blade with the apex thereof substantially coinciding with the stagnation point of the flow to produce on both blade surfaces a spanwise component of direction toward the same end of the blade for discharging fluid tangentially along the exposed surface of said succeeding platelet from within the blade with substantial spanwise. aswell as chordwise components of velocity providing for a flow of fluid across the exposed surface of each said platelet, the wall of said tube being perforated to provide communication between said slots. and said tube interior.

3. In. combination toform a slotted, turbine blade, a sheet. metal tube having a blade cross section, and inclined spaced platelets disposed spanwise along the'nose portion of said tube, said platelets being curved inthe chordwise direction, each said platelet lapping a succeeding platelet to: form. a slot' therebetween having legs. on both upper and lower surfaces ofthe blade with the apex thereof substantially coinciding; with the stagnation point of the flow to produce on both blade surfaces a spanwise component of direction toward the same end of the blade-fordischarging fluid tangentially along the exposedsurfaces of succeeding platelets on both upper andxloiwer blade surfaces with substantial axial and. chordwise components of velocity providing for a flow of fluid'across' the exposed surfaceof each said platelet, the wa l of said tub'e'beingperforated tov provide communication between said slots and said tube interior. a

4. In combination to form a slotted turbine blade, a sheet metal tube having a blade. cross section, and inclinedspaced platelets disposed spanwise along the nose portion of said tube, each. said platelet being curved in the chordwise direction and having an oval-like contouigeach said platelet lapping an axially succeedingvplatelet to define slots therebetween, the exits of said slots defining aplurality of. chevron shaped lines distributed along the blade nose with the apex thereof at substantially the stagnation point of the flow, and means to supply fluid to the spaces between p-latelets'for discharge over the exposed surface of each of the platelets to insulate it 5. In combination, to form a slottedturbine blade, spaced walls enclosing a hollow' interior and shaped to a blade; contour and having upper and lower exposed surfaces, anose porti'onjoining said walls at the forward end of said blade,-

means on said blade defining a plurality ofspanw se spaced slots extending generally transversely of said nose portion and adapted to discharge a series of overlapping air jets in protective relation to the surface thereof, said blade having an opening into its hollow interior to admit a fiow of fluid for discharge through said slots, said slots having inclined legs extending to the upper and? v lower surfaces of said blade with a spanwisecomponent of direction on each said surface toward the same end of the blade and meetin in an apex located substantially at the stagnation point of the flow.

6. In combination. to form a slotted turbine blade, spaced walls enclosing a hollow interior and shaped to a blade contour and having upper and lower exposed surfaces, a nose portion joining said wallsat the forward end of said blade, means on said'blade defining a plurality of spanwise spaced slots extending generally transversely, of said nose portionand adapted to discharge a series of overlapping air jets in protective relation to the surface thereof, said blade having an opening at one end thereof into its hollow interior to admit a'flow of fluid for discharge through said slots said slots being substantially chevron-shaped and extending to the upper and lower surfaces of said blade with the apex substantially at the stagnation point and with each leg having a spanwise component of direction on each said surface away from the end of said blade having said fluid admission opening.

EDWARD A. STALKER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Stalker -4 Sept. 11, 1951 

